The goal of this project is to provide support of National Toxicology Program (NTP) hazard identification activities targeted toward the prevention of adverse effects caused by exposure to AIDS therapeutics. Toxicity testing is an important aspect of public health research in that it serves to identify chemicals that are hazardous to human health. Proper chemical analyses are required to ensure that, in toxicity studies, the test species are exposed to the prescribed chemicals at the specified dose concentrations. This contract contributes to the ability of toxicity studies to provide evidence of heightened cancer risk along with other toxicological outcomes, by providing characterization of the chemicals studied, confirmation of the dose levels administered, and internal dose determinations. This information is critical to evaluation of toxicity tests and development of sound, scientific conclusions about the potential toxicity of the study chemical in the test species and ultimately supports the risk assessment efforts of National Toxicology Program and other federal agencies. With internal dose information provided by this contract, extrapolations to humans can be made so that the public can be adequately informed about risk factors arising from exposure to studied chemicals. During FY10 more than 16 tasks were begun, performed, and/or completed in support of NTP and DIR AIDS research and testing protocols. The chemistry contractor completed consolidation of stored lots of AZT, 3TC, ddI, ddC, and ddA, and the associated characterization effort. The chemistry support contractor procured and began the comprehensive characterization of 4 new AIDS therapeutics during the reporting period. UPLC, gas chromatography, elemental analysis were used to assess the purity of emtricitabine, lopinavir, ritonavir, and tenofovir. In the coming months dose formulation preparation and analysis methods will be developed for the later compounds individually and in combination.